Effects of Waterlogging Stress on Growth and Physiological Index in Cucumber Seedlings

The effects of waterlogging stress on the growth, chlorophyll and MDA content of cucumber seedlings were studied by using cucumber varieties （Cucumis sativus L. cv. Jinyan No.7） as materials. The results show that plant height, leaf number, shoot fresh weight, total root length, total projected area and total surface area of cucumber seedlings showed insignificant differences with those of the control; root fresh weight, root average diameter, total root volume were significantly higher, but the number of root tips and furcation number increased first and then reduced; the chlorophyll content of cucumber seedlings was significantly lower than that of control; MDA content was significantly higher than that of control under waterlogging stress. It was showed that the cucumber was tolerant to waterlogging stress, but the ability of waterlogging stress was limited, and the physiological was significantly hurt and photosynthesis of cucumber seedlings was significantly affected by waterlogging stress.

Effects of Waterlogging Stress on the Physiological Characteristics and Secondary Metabolites of Herbaceous Peony (<i>Paeonia lactiflora</i>Pall.)

Herbaceous peony is an ornamental plant with medicinal properties. Waterlogging can affect its yield and quality as it grows and matures. In this study, we subjected “Taohuafeixue”, “Yangfeichuyu” and “Hongxiuqiu” herbaceous peony varieties to a simulated waterlogging stress treatment and investigated the effects of waterlogging on their physiological characteristics and the secondary metabolite contents in their leaves and roots. Short-term waterlogging caused the leaves to turn yellow or red and the roots to turn black. The stele and the cell wall of the endothelial cells thickened, and the cortical cells enlarged. Waterlogging did not significantly change plant height, leaf length, and leaf area;however, it significantly decreased the root-shoot ratio of “Yangfeichuyu” and “Hongxiuqiu” varieties. The activity of antioxidant enzymes and the content of osmotic regulators increased under waterlogging. After short-term waterlogging stress treatment, the content of paeoniflorin and albiflorin increased in the roots of “Taohuafeixue” and “Yangfeichuyu”, and the content of benzoylpaeoniflorin increased in the root of “Hongxiuqiu”. The content of gallic acid and total flavonoids increased in the leaves of “Taohuafeixue” and “Yangfeichuyu”. After the waterlogging, paeoniflorin and benzoylpaeoniflorin increased in the autumn root of “Hongxiuqiu”. This study expands our knowledge about the medicinal properties of herbaceous peony and informs about its production and cultivation under waterlogged conditions.

Comparison of Morphological and Anatomical Characteristics of Taxus chinensis var.mairei Seedlings Root under Waterlogging Stress in Different Substrates

Four different ratios of river sand,ceramic pellets,vermiculite and perlite(1:1),and field soil were selected as the substrates in this experiment,and four gradient levels of root waterlogging,half waterlogging,full waterlogging and normal were set to investigate the effects of different gradients of waterlogging stress on the root morphology of Taxus chinensis var.mairei seedlings under different substrates.In this study,the root anatomical structure of Taxus chinensis var.mairei under different waterlogging stress was observed by the paraffin section method.The roots of T.chinensis var.mairei were diarch,with no pith and resin canals.There was a large number of tannins in the pericycle of the aerial adventitious roots of seedlings adapted to waterlogging.Also,the endodermis has obvious casparian strip thickening,and there were 4-5 layers of large parenchymatous cells in the close to the inner side of the pericycle in the vascular cylinder,which could increase the storage capacity,and transport capacity of the root.Under the treatment of root waterlogging stress,the development of plant roots in the mixed substrate of vermiculite and,perlite was the earliest.Under half waterlogging stress,T.chinensis var.mairei seedlings treated with various substrates all could better adapt to the environment of waterlogging stress.Under the stress of fully waterlogging,the roots of seedlings planted in river sand substrate developed secondary growth.

Changes of Antioxidative Enzymes and Lipid Peroxidation in Leaves and Roots of Waterlogging-Tolerant and Waterlogging-Sensitive Maize Genotypes at Seedling Stage

To better understand the physiological and biochemical mechanisms of waterlogging tolerance, waterlogging effects on lipid peroxidation and the activity of antioxidative enzymes were investigated in leaves and roots of two maize genotypes, HZ32 （waterlogging-tolerant） and K12 （waterlogging-sensitive）. Potted maize plants were waterlogged at the second leaf stage under glasshouse conditions. Leaves and roots were harvested 1 d before and 2, 4, 6, 8 and 10 d after the start of waterlogging treatment. Through comparing the activities of superoxide dismutase （SOD）, ascorbate peroxidase （APX）, glutathione reductase （GR）, catalase （CAT） and guaiacol peroxidase （POD） between waterlogging-tolerant and waterloggingsensitive genotype, we deduced that CAT was the most important H2O2 scavenging enzyme in leaves, while APX seemed to play a key role in roots. POD, APX, GR and CAT activities in conjunction with SOD seem to play an essential protective role in the O2^- and H2O2 scavenging process. Lipid peroxidation was enhanced significantly only in K12 （P 〈 0.001） and there was no difference （P 〉 0.05） in HZ32 up to 6 d after waterlogging stress. These results indicated that oxidative stress may play an important role in waterlogging-stressed maize plants and that the greater protection of HZ32 leaves and roots from waterlogging-induced oxidative damage results, at least in part, through the maintenance of increased antioxidant enzyme activity.

Waterlogging tolerance and wood properties of transgenic Populus alba×glandulosa expressing Vitreoscilla hemoglobin gene(Vgb)

Because overexpression of Vitreoscilla hemoglobin gene(Vgb)gene in plants can enhance tolerance to waterlogging,here Vgb was inserted into Populus alba×glandulosa to investigate its expression and effects on growth and physiological responses to waterlogging stress in the transgenic poplars.Southern blotting and RT-PCR analysis of Vgb-transgenic P.alba×glandulosa showed that the Vgb gene was integrated into the genome of the V13-81 and V13-85 transgenic lines and expressed.In greenhouse waterlogging stress tests,mortality of the transgenic poplar was significant lower than that of nontransgenic plants with increasing treatment time from 2 to 22 days.The transgenic plants had higher chlorophyll content and less chloroplast damage than in the control plants.Additionally,starch accumulation increased,and growth was enhanced in the transgenic plants,suggesting that the Vgb-expressing lines had improved energy reserves.Field trials of the transgenic poplar suggested that Vgb expression promotes growth and influences wood quality.Taken together,our results suggest that the expression of Vgb can increase the accumulation of chlorophyll and starch in the transgenic poplar,improve its ability to endure flooding,and improve growth and wood quality of the transgenic plants.

Preliminary Study on the Waterlogging Tolerance of 116 Corn Materials

Maize is one of the most important food crops in the world.With the global warming,waterlogging stress has become an important abiotic stress factor that affects crop growth,including maize.Waterlogging seriously affects 10%of the arable land and can lead to a 15%-80%reduction in crop yield[1].In this study,115 inbred line materials commonly used in spring maize planting areas in the Jianghan Plain,Hubei,and maize inbred line B73 with complete genome information,were collected and stressed by waterlogging for two weeks in the seven-leaf and one-heart stage,and the survival rate was statistically compared and analyzed,aiming to screen germplasms with strong waterlogging tolerance for the genetic improvement of waterlogging tolerance of Hubei maize lines.